Process for the production of planographic printing plates having an aluminum support



United States Patent 3,223,524 PROCESS FUR THE PRODUCTIQN OF PLANO- GRAPHIC PRINTING PLATES HAVING AN ALUMINIUM SUPPQRT Anita von Kt'inig, Leverkusen, Germany, assignorto Agfa Aktiengeselischaft, Leverkusen, Germany, a corporation of Germany No Drawing. Filed Sept. 26, 1960, Ser. No. 58,181

5 Claims. (CI. 96-29) The invention relates to a method for improving planographic printing plates having an aluminium support.

It is known that photographically produced silver images can be transformed into heavy metal and/or silver salt images by oxidation. The resulting images can be reacted with an organic compound containing an SH-, SeH- or NH-group to produce sparingly soluble salt like compounds which take up greasy printing inks.

It is also known that photographic silver images can be deposited by the silver salt diffusion process on to unprepared aluminium plates having a rough surface and which are suitable for planographic printing. The silver images can be made water-repellent by treating them with an organic compound which is capable of being adsorbed by metallic silver so as to render the images capable of taking up greasy printing inks. In this way planographic printing plates are obtained. Suitable organic compounds which are capable of being adsorbed by metallic silver described in the copending application Serial No. 730,259, now US. Patent 3,083,097, are 2,5-dimercapto-1,3,4-thiodiazole, S-mercapto-B-phenyl- 1,3,4-thiodiazo1ethione-2,5 mercaptotetrazole, l-p'henyl- S-mercaptotetrazole, 3-mercapto-1,2,4-triazole, l-phenyl- 3-mercapto-l,2,4-triazole, 2,4,6-trimercapto-1,3,5-triazine, 2-mercapto-4,5-dimethyl-fi-oxypyrimidine, 6 mercaptopurine, tetraethyl thiuram disulphide, thiourea, phenyl thiourea, phenyl thiosemicarbazide, diphenyl thiosernicarbazide, diphenyl thiocarbazone, diphenyl carbazide and compounds of the general formula wherein R represents an alkyl radical, X represents an NH group or an oxygen or sulphur atom and Y represents an oxygen or sulphur atom.

The aforementioned componds, however, do not in many cases impart a sufiicient water-repellent character to the silver images.

Either the color absorption is too small on account of the water-repelling effect being too weak, or in certain cases where the color absorption is good the silver images which have been made water-repellent are unstable with respect to atmospheric influences and with respect to dilute phosphoric acid. images which have been made water-repellent have a high resistance to atmospheric influences since the planographic printing plates have to be stored in the printing works for several hours or even days. The planographic printing plates must also be resistant to dilute phosphoric acid, because the printing inks and moistening mechanisms of the printing machines and also the sponges used for rubbing down the fixing contain phosphoric acid.

It is essential that the silver ice For practical reasons it is preferable if the organic compounds employed for the purpose of making the silver images water-repellent are soluble or are capable of being suspended in the fixing solutions normally employed in planographic printing. Especialy suitable are aqueous solutions'ofgum arabic, polyvinyl alcohol and carboxymethyl cellulose, which are adjusted to a pH of from 4 to 6 by means of phosphoric acid or a phosphate. This adjustment of the pH is effected in the absence of an organic solvent, since organic solvents dissolve the printing inks.

It has now been found that silver images which have been produced on aluminium plates by the silver salt diffusion process can be renderedcapable of takin-gup ink satisfactorily if there is used for producing the water-repellent effect a solution or suspension containing a derivative of Z-mercapto-1,3,4-thiodiazole which contains at least two mercapto groups and at least two 1,3,4-thiodiazole radicals bonded by way of an organic radical. Especially suitable are compounds of the general formula N'-Ifi1 NN HS-(l wherein Z stands for (I) alkylene with 1 to 6 carbon wherein n is an integer, preferably from 1 to 5, and m is an integer from 2 to 4, or (III) NH.B.NH', wherein B stands for alkylene with 4 to 10 carbon atoms, cycloalkylene or arylene.

The compounds of the type are described in Chemical Abstracts 1960, 1502b, respectively Journal of Chemical Society (Jap), Pure Chemical Section 78 (1957), 1588 to 1591. The melting points of some of said compounds are given in the following Table 1:

TABLE 1 Compound Number of CH -groups Melting point, deg.

n=0 292293 n=2 280-283 n=4 3 4 The compounds of the type The yield is 48 g. with a melting point of 273. The N N N melting points of some of the compounds prepared H H ll H in this way are given in Table 3 HSG CS.A.SC\ CSH s s 5 TABLE 3 can be prepared as follows:

2 mols of 2,5-dirnercapto-1,3,4-thiodiazole are dissolved Compound -B Melting point, dog. in a solution of 2 mols of sodium or potassium hydroxide in 1200 cc. of aqueous alcohol (85% by volume). 1 mol xv orri i- 198-199 of an ot,w-dihalogenoalkane is added to this solution. The solution is boiled for 2 to 6 hours under reflux and, XVI 271-273 after cooling, the precipitated product is suction-filtered and washed free from halogen. The yield is 85 to 95%. Q The product is purified by recrystallization from alcohol XVII QHOO or by being repeatedly dissolved and crystallized. The melting points of some of the compounds prepared in XVIII this way are given in the following Table 2:

m Compound A Melting point, deg. The compounds are suspended, with the and of emulsi- CH2' 174-176 fiers, in an aqueous alkali solution or in the fixing solu- 214-216 tions normally employed in planographic printing. The '(CH2)3 162-163 --(CH2)4 191-193 compounds are generally employed in an amount of from 162163 5 to 20 g./l. The silver images produced in known (CH 145-147 (CHE)IU 131-132 manner on an aluminium foil having a rough surface by the silver salt diffusion process are made water-repellent CHg-cHT 223 by coating them with the aforementioned solutions or suspensions. CH: It is also possible to use a solution of one of the aforementioned compounds and the acid fixing solution sucxrr -CHz oH= 220 cessively in separate working steps.

I It is, however, more desirable to combine the com- H3 pounds with a fixing solution known as per se in con- XIII onionioon,cn 80 nection with planographic printing using aluminium XIV 'CH2CH2OCH2CHIOCH2CHZ 105-106 plates, for example with an aqueous solution of gum arabic, polyvinyl alcohol, carboxymethyl cellulose, de- A compound of the type 40 rivatives of alginic acid such as alkaline salts, amides and N N esters and caragheenate (extracts of red seaweed, de-

ll l scribed in Melliand Textilbrichte 1960, pages 596 to 600 HS O /E SH and 861 to 865), which is adjusted by means of phos- S phoric acid or a phosphate to a pH of from 4 to 6. After can b prepared as f ll the silver image has been made water-repellent and the 025 mol) f 4 4' 1 4 1 h 1 i hi plate has been fixed, which operations take place simulsemicarbazide are dissolved in 600 cm. dimethyl formlh the P Ink 1S pp amide. While stirring em. of carbon disulphide are by g 0r rolhpg y g p by the p ps p added dropwise to this solution at room temperature. The Prmtlng Portlofls fllstlflglllshed y a hlgh bI 1d1ng The solution is heated to 65 0. within minutes and 50 Strength for greasy prmtmg About 5000 satlsfackept at this temperature for 20 hours until the develop- 'Y P can be producedment of hydrogen sulphide is finished. The product is In Order to P F stablesuspenswns of the precipitated by stirring the reaction mixture into aqueous Pounds 111 the acid fiXlng sollltlons, the Compounds must hydrogen chloride which is cooled with ice. The precipibe emulsified by means of emulsifiers, preferably anionictated product is suction-filtered and washed free from 55 active emulsifiers. Suitable emulsifiers and emulsifyhalogen. The raw material is purified by reprecipitation. ing auxiliaries are given in Table 4.

TABLE 4 Emulsifier Name Constitution Manul'acturer Monopolbrillaut6l Sulphonate castor Oil stfkllliilscn & Co.

6 Teepol Sec. alkyl Sulphate Shell. 9

Sodium oleoylisaethionate Hoochster Farbwcrke. Acid diethylamino oleate Fairbeufaxnren 8. e 5 Tamol NNO Dinaphthylmethane Bad. Ai 1i1i.n u.Sodasulphonate. Fabrik. 6 Humcctol C Dibutylamide of sul- Casella-Farbwerke.

phonated rioinoleic acid. Polyglycol P 400--.. Hoechster Farbwerke. Texapon Z (high Sulphate of coconut fatty Dehydag.

cone.) alcohol. Polystate Monoand dlstearate oi SOG EP.

polyethylene glycol 300. Emulgator NP 10--. Farbenfabriken Bayer A.G. Tween 40 Polyethylene sorbitnne Atlas-Goldschnn'dt monopalmitate. G.m.b.H. Emulgator 157 Propylenglycol monoand Atlas-Goldsehmidt distearate. G.In.b.H.

Examlple 1 50 g. of the aforementioned compound V (see Table 2) are suspended in 100 cc. of Emulgator (i.e. Table 4 #4), preferably in a mixing apparatus, for example in a cutting mill, vibrating mill, high-pressure homogenizer, a turbulence chamber equipped with a high speed stirrer or a roll stand having three rollers. The homogeneous suspension is dispersed in 4900 cc. of a 10% aqueous polyvinyl alcohol solution and the dispersion is adjusted to a pH of 4.4 by means of 10% phosphoric acid. A silver image produced on an aluminum offset plate by the silver salt diffusion process is rubbed with the above dispersion. The excess dispersion is wiped off with a moist sponge, whereupon the plate is used for printing.

Example 2 75 g. of the aforementioned compound IV (see Table 2) are suspended in 150 cc. of a 50% aqueous solution of Monopolbrillantol (i.e. Table 4, #1) in a mixing apparatus. The homogeneous mixture is dispersed in 4850 cc. of a 7% aqueous carboxymethyl cellulose solution. The dispersion is adjusted to a pH of 5.2 by means of 10% phosphoric acid. The dispersion is employed as in Example 1.

Example 3 100 g. of the aforementioned compound X (see Table 2) are mixed with 20 cc. of Teepol (20%, normal commercial type), 200 cc. of polyglycol P 400 and 100 g. of aqueous gum arabic solution (1:1) in a ball mill for 3 hours. The homogeneous mixture is dispersed in 4800 cc. of a 2.0% aqueous carboxymethyl cellulose solution and the dispersion is adjusted to a pH of 4.6 by means of 10% phosphoric acid. The dispersion is employed as in Example 1.

Example 4 .50 g. of the aforementioned compound VII (see Table 2) are mixed with 7.5 cc. of Teepol, 50 cc. of Polyglycol P 400 and 50 cc. of a 10% aqueous solution of Luviskol K 90 (polyvinyl pyrrolidone, molecular weight about 700,000, manufactured by BSAF) in a mixing apparatus and dispersed in 4900 cc. of a 2.5% aqueous carboxymethyl cellulose solution. The dispersion is adjusted to a pH value of 4.1 With 10% phosphoric acid. The dispersion is employed as in Example 1.

Example 5 A silver image produced on an aluminium offset plate by the silver salt diffusion process is treated with a solution of 5 g. of the aforementioned compound VI (see Table 2) dissolved in 100 cc. of 1.8% caustic potash solution. After the plate has been made water-repellent in this way, it rubbed with a 25% aqueous gum arabic solution which is adjusted to a pH value of 4.0 with phosphoric acid. The plate is then used for printing.

Example 6 40 g. of the aforementioned compound V (see Table 2) are suspended in 100 cc. of 2% aqueous solution of Tamol NNO and then dispersed in 4900 cc. of a aqueous Luviskol K 90 solution (BASF), which is adjusted to a pH value of 4.3 with 10% phosphoric acid. The resulting dispersion is employed as in Example 1.

Example 7 50 g. of the aforementioned compound VII (see Table 2) are suspended in 2.5 cc. of Teepol, 2.5 cc. of 20% Hostapan A and 100 cc. of Polyglycol P 400. The resulting suspension is dispersed in 4900 cc. of 2.5% aqueous carboxymethyl cellulose solution and the pH of the dispersion is adjusted to 4.1 with phosphoric acid. The dispersion is employed as in Example 1.

Example 8 60 g. of the aforementioned compound VI (see Table 2) are suspended in 6.0 cc. of highly concentrated Texapon Z (20% aqueous solution) and 150 cc. of Polyglycol P 400. The resulting suspension is dispersed in 4850 cc. of a 2% aqueous solution of sodium alginate (Algipon P III solution, Henkel & (10.), which contains 436 g. of primary potassium phosphate and 48.5 g. of secondary sodium phosphate and which has a pH value of 5.7. The dispersion is employed as in Example 1.

Example 9 50 g. of the aforementioned compound VII (see Table 2) are mixed with 10 cc. of a 20% solution of the Teepol (see Table 4) and cc. of a 1.5% aqueous solution of propylene glycol ester of alginic acid in a mixing apparatus and are dispersed in 4890 cc. of a 1% solution of the above mentioned alginic acid ester. The dispersion is employed as in Example 1.

Example 10 60 g. of the aforementioned compound VII (see Table 2) are mixed with 12 cc. of a 10% aqueous solution of the Texapon Z (see Table 4) and cc. of a 1.5% aqueous solution of the amide of alginic acid in a mixing apparatus. Said mixture is dispersed in a mixture of 1850 cc. of a 1% aqueous solution of propylene glycol ester of alginic acid and 3000 cc. of a 2% aqueous solution of carboxymethyl cellulose. The pH value of the dispersion is adjusted to 4.1 with 10% phosphoric acid.

Example 11 50 g. of the aforementioned compound II (see Table 1) are mixed with 10 g. of the Polystate (see Table 4), 25 cc. Polyglycol P 300 and 50 cc. of a 1% aqueous solution of caragheenate in a mixing apparatus and dispersed in 4900 cc. of a 1% aqueous solution of caragheenate. The dispersion is employed as described in Example 1.

Example 12 70 g. of the aforementioned compound XII (see Table 2) are suspended in 35 g. of the Tween 40 (see Table 4) and 50 cc. Polyglycol P 600 and dispersed in 4900 cc. of a 2.5% aqueous solution of carboxymethyl cellulose. The dispersion is adjusted to a pH value of 4.3 with phosphoric acid. The resulting dispersion is employed as disclosed in Example 1.

Example 13 Example 14 50 g. of the aforementioned compound XI (see Table 2) are suspended in 25 g. of the Texapon Z (see Table 4), 25 cc. of Polyglycol P 300 and 50 cc. of a 1% aqueous solution of caragheenate. This suspension is dispersed in 4900 cc. of a 1.5% aqueous solution of the propylen glycol ester of alginic acid. The dispersion is employed as described in Example 1.

What I claim is:

1. A planographic printing form comprising an aluminium plate having superimposed thereon at least one image consisting essentially of silver particles, said image being rendered hydrophobic and receptive to greasy pn'nt ing inks by the direct application thereon of an effective amount of a 2-mercapto -1,3,4-thiodiazole having the formula wherein Z stands for a bivalent member selected from the group consisting of (1) alkylene having up to 6 carbon atoms; (II) --SAS, wherein A is a member selected from the group consisting of alkylene of 1-10 carbon atoms, phenyla'lkylene, [CH --(CH wherein m is 2-4 and n is 1-4; and (HI) NHBNH wherein B is a member selected from the group consisting of alkylene of 4-10 carbon atoms, cyclohexylene, phenylene, diphenylene, and phenylalkylene.

2. A process for producing planographic printing plates consisting in developing an imagewise exposed silver halide emulsion layer while in contact with an aluminum plate in a silver halide developer solution containing a silver "halide solvent for dissolving silver halide from the unexposed areas of said silver halide emulsion layer, transferring the dissolved unexposed silver halide to said aluminum plate and reducing the dissolved silver halide on said aluminium plate to obtain a corresponding silver image, characterized in thereafter contacting said silver image directly with a hydrophobing amount of a Z-mercapto- 1,3,4-thiodiazole having the formula N HS("3 (i-z-ii -HS wherein Z stands for a bivalent member selected from the group consisting of (I) alkylene having up to 6 carbon atoms; (II) SAS-, wherein A is a member selected from the group consisting of alkylene of 1-10 carbon atoms, phenylalkylene, [(CH O(CH wherein m is -2-4 and n is 1-5; and (III) NHBNH- wherein B is a member selected from the group consisting of alkylene of 4-10 carbon atoms, cyclohexylene, phenylene, diphenylene, and phenylalkylene.

3. The process of claim 2, wherein the silver image is treated with a dispersion containing, in addition to the thiodiazole at least one product selected from the class consisting of carboxymethyl cellulose, polyvinyl alcohol, gum arabic, alginic acid, alkali salts of alginic acid, amides of alginic acid, esters of alginic acid and caragheenates; and a member selected from the class consisting of phosphoric acid and acid water-soluble phosphates.

4. The process of claim 2, wherein the silver images are treated with a dispersion which has been prepared with the aid of emulsifiers and emulsifying auxiliaries.

5. The process of claim 2, wherein the silver image is treated with a dispersion containing the thiodiazole derivative and additionally an organic hydrophilic film-forming product which is soluble in said dispersion, and a member selected from the class consisting of phosphoric acid and acid water-soluble acid phosphates.

References Cited by the Examiner UNITED STATES PATENTS 2,184,288 12/1939 Dangelmajer 9633 2,352,014 6/1944 Rott 9629 2,514,650 7/1950 Knott et al. 9652 2,685,588 8/1954 Goshorn et al. 260-302 2,891,961 6/1959 Turner et al 260306.8 3,083,097 3/1963 Lassig et al 9629 FOREIGN PATENTS 572,336 4/1959 Belgium.

582,160 3/ 1960 Belgium.

582,161 3/1960 Belgium.

760,181 10/1956 Great Britain.

OTHER REFERENCES Chemical Abstracts 54, l502d (1960).

NORMAN G. TORCHIN, Primary Examiner.

PHILIP E. MANGAN, Examiner. 

2. A PROCESS FOR PRODUCING PLANOGRAPHIC PRINTING PLATES CONSISTING IN DEVELOPING AN IMAGWISE EXPOSED SILVER HALIDE EMULSION LAYER WHIE IN CONTACT WITH AN ALUMINUM PLATE IN A SILVER HALIDE DEVELOPER SOLUTION CONTAINING A SILVER HALIDE SOLVENT FOR DISSOLVING SILVER HALIDE FROM THE UNEXPOSED AREAS OF SAID SILVER HALIDE EMULSION LAYER, TRANSFERRING THE DISSOLVED UNEXPOSED SILVER HALIDE TO SAID ALUMINUM PLATE AND REDUCING THE DISSOLVED SILVER HALIDE ON SAID ALUMINIUM PLATE TO OBTAIN A CORRESPONDING SILVER IMAGE, CHARACTERIZED IN THEREAFTER CONTACTING SAID SILVER IMAGE DIRECTLY WITH A HYDROPHOBING AMOUNT OF A 2-MERCAPTO1,3,4-THIODIAZOLE HAVING THE FORMULA 